This disclosure relates to polyester compositions, processes of manufacture, and articles thereof.
Polyesters, copolyesters, and their blends with other thermoplastics have a number of advantageous properties, in particular high mechanical strength and good processability, which make them useful in a wide variety of applications. Nonetheless, there remains a long felt need for methods for improving specific property combinations in polyester compositions, compositions (and articles made from the compositions) that exhibit a certain combination of useful properties, regardless whether the composition is subjected to an injection molding process or a blow molding processes. One such combination is good low temperature ductility, low permeability, and chemical resistance. A combination of low temperature ductility, low permeability, and good chemical resistance would be useful for articles that are manufactured by injection or blow molding processes. These features are especially useful for fuel tanks, such as gasoline containers, which must remain in contact with fuels for extended periods. These tanks are often manufactured by blow molding.
Unfortunately, ordinary technology and available information has been unable in disclosing or teaching polyester compositions that exhibit a combination of low temperature ductility and good chemical resistance and low permeability that are manufactured by injection or blow molding processes. Blow-molding processes are typically more demanding process than injection molding processes, because, in part, the conditions created by blow molding processes subject the molten polymer to air for relatively longer periods of time than injection molding processes-factors that have been known to adversely affect the properties of the compositions and the articles made from them. Improvements in low temperature ductility, for instance by addition of rubbery impact modifier or ductile polymer such as polycarbonate have been found to degrade the chemical resistance and low permeability of polyester compositions, and conversely, improvements in chemical resistance, particularly to fuels and/or short chain alcohols, have been found to worsen low temperature ductility. Further, regulatory changes have created the need for improved polymers that exhibit a useful combination of low temperature ductility, good chemical resistance, and low permeability when exposed to gasoline, biofuels such as ethanol-containing fuels, and other new fuels.
For the foregoing reasons, there remains a need in the art for polyester compositions that have improved low temperature ductility and good chemical resistance, particularly when articles formed from the compositions are blow molded.